A team of gene therapy researchers has reported positive results in a phase 1/2 clinical trial for the inherited bleeding disorder hemophilia B. A single intravenous infusion of a novel bioengineered gene therapy enabled adult participants to safely produce sustained levels of clotting factor that prevented debilitating bleeding episodes. Patients were able to terminate prophylactic treatments; the gene therapy nearly universally eliminated their need for intravenous infusions of manufactured clotting factor.